Spray-on plasmonics create tunable colours at video speeds

Researchers have leveraged plasmonics to create stable colors. The colors can be electrically tuned across different wavelengths, at video-fast speeds. This can be used for next-generation display screens.

Plasmonic metasurfaces could open the door to more sophisticated flat panel display applications. This is due to the full color gamut and high spatial resolution that the technology promises. A plasmon is a quantum of plasma oscillation; and plasmonics is the study of collective oscillations of free electron gas density - the type of technology that is used for plasma display screens.

A current limitation with plasmonics is due to the complexity in tuning the colors, which is something that requires expensive lithographic techniques. To overcome this challenge, University of Cambridge scientists have developed a scalable electrically driven color-changing metasurface. The process controls plasmonic gaps and fills them with an active medium. This medium is formed of electrochromic nanoparticles, which are coated onto a metallic mirror. This creates the smallest-area active plasmonic pixels yet designed.

According to principal researcher Professor Jeremy J Baumberg: "These are not the normal tools of nanotechnology, but this sort of radical approach is needed to make sustainable technologies feasible. The strange physics of light on the nanoscale allows it to be switched, even if less than a tenth of the film is coated with our active pixels. That's because the apparent size of each pixel for light is many times larger than their physical area when using these resonant gold architectures."

The process is described as forming nanoparticles-on-mirror, since the particles are coated onto a metallic mirror. These particles strongly confine light within the individual gaps to the underlying mirror. This serves to produce very localized cavity resonances and precisely tuned colour scattering, which is independent and insensitive to the angle and polarization of incident light.

These nanopixels have been shown to produce an effective scattering of colors and they are electrically tunable across >100-nm wavelength ranges. This could leas to the production of a new generation of displays, which are hundredfold thinner than current displays on the market. Such is the scalability of the technology, this could extent to large-scale flexible displays, big enough to cover entire buildings.

The innovation has been published in the journal Science Advances, with the research paper headed “Scalable electrochromic nanopixels using plasmonics.”